58 research outputs found
Generation of Mutants from the 57B Region of Drosophila melanogaster
The 57B region of Drosophila melanogaster includes a cluster of the three homeobox genes
orthopedia (otp), Drosophila Retinal homeobox (DRx), and homeobrain (hbn). In an attempt to isolate mu tants for these genes, we performed an EMS mutagenesis and isolated lethal mutants from the 57B
region, among them mutants for otp, DRx, and hbn. With the help of two newly generated deletions
from the 57B region, we mapped additional mutants to specific chromosomal intervals and identi fied several of these mutants from the 57B region molecularly. In addition, we generated mutants
for CG15651 and RIC-3 by gene targeting and mutants for the genes CG9344, CG15649, CG15650,
and ND-B14.7 using the CRISPR/Cas9 system. We determined the lethality period during develop ment for most isolated mutants. In total, we analysed alleles from nine different genes from the 57B
region of Drosophila, which could now be used to further explore the functions of the corresponding
genes in the future
The Kr85 s-process Branching and the Mass of Carbon Stars
We present new spectroscopic observations for a sample of C(N)-type red
giants. These objects belong to the class of Asymptotic Giant Branch stars,
experiencing thermal instabilities in the He-burning shell (thermal pulses).
Mixing episodes called third dredge-up enrich the photosphere with newly
synthesized C12 in the He-rich zone, and this is the source of the high
observed ratio between carbon and oxygen (C/O > 1 by number). Our spectroscopic
abundance estimates confirm that, in agreement with the general understanding
of the late evolutionary stages of low and intermediate mass stars, carbon
enrichment is accompanied by the appearance of s-process elements in the
photosphere. We discuss the details of the observations and of the derived
abundances, focusing in particular on rubidium, a neutron-density sensitive
element, and on the s-elements Sr, Y and Zr belonging to the first s-peak. The
critical reaction branching at Kr85, which determines the relative enrichment
of the studied species, is discussed. Subsequently, we compare our data with
recent models for s-processing in Thermally Pulsing Asymptotic Giant Branch
stars, at metallicities relevant for our sample. A remarkable agreement between
model predictions and observations is found. Thanks to the different neutron
density prevailing in low and intermediate mass stars, comparison with the
models allows us to conclude that most C(N) stars are of low mass (M < 3Mo). We
also analyze the C12/C13 ratios measured, showing that most of them cannot be
explained by canonical stellar models. We discuss how this fact would require
the operation of an ad hoc additional mixing, currently called Cool Bottom
Process, operating only in low mass stars during the first ascent of the red
giant branch and, perhaps, also during the asymptotic giant branch.Comment: 54 pages + 6 figures + 6 tables. ApJ accepte
Oxygen Abundances in Two Metal-Poor Subgiants from the Analysis of the 6300 A Forbidden O I Line
Recent LTE analyses (Israelian et al. 1998 and Bosegaard et al. 1999) of the
OH bands in the optical-ultraviolet spectra of nearby metal-poor subdwarfs
indicate that oxygen abundances are generally higher than those previously
determined. The difference increases with decreasing metallicity and reaches
delta([O/Fe]) ~ +0.6 dex as [Fe/H] approaches -3.0.
Employing high resolution (R = 50000), high S/N (~ 250) echelle spectra of
the two stars found by Israelian et al. (1998) to have the highest
[O/Fe]-ratios, viz, BD +23 3130 and BD +37 1458, we conducted abundance
analyses based on about 60 Fe I and 7-9 Fe II lines. We determined from Kurucz
LTE models the values of the stellar parameters, as well as abundances of Na,
Ni, and the traditional alpha-elements, independent of the calibration of color
vs scales. We determined oxygen abundances from spectral synthesis of
the stronger line (6300 A) of the [O I] doublet.
The syntheses of the [O I] line lead to smaller values of [O/Fe], consistent
with those found earlier among halo field and globular cluster giants. We
obtain [O/Fe] = +0.35 +/- 0.2 for BD +23 3130 and +0.50 +/- 0.2 for BD +37
1458. In the former, the [O I] line is very weak (~ 1 mA), so that the quoted
[O/Fe] value may in reality be an upper limit.
Therefore in these two stars a discrepancy exists between the [O/Fe]- ratios
derived from [O I] and the OH feature, and the origin of this difference
remains unclear. Until the matter is clarified, we suggest it is premature to
conclude that the ab initio oxygen abundances of old, metal-poor stars need to
be revised drastically upward.Comment: 38 pages, 5 tables, 14 figures To appear in July 1999 AJ Updated
April 16, 1999. Fixed typo
The Essential Elements of a Risk Governance Framework for Current and Future Nanotechnologies
Chemical Compositions of Red Giant Stars in Old Large Magellanic Cloud Globular Clusters
We have observed ten red giant stars in four old Large Magellanic Cloud
globular clusters with the high-resolution spectrograph MIKE on the Magellan
Landon Clay 6.5-m telescope. The stars in our sample have up to 20 elemental
abundance determinations for the alpha-, iron-peak, and neutron-capture element
groups. We have also derived abundances for the light odd-Z elements Na and Al.
We find NGC 2005 and NGC 2019 to be more metal-rich than previous estimates
from the Ca II triplet, and we derive [Fe/H] values closer to those obtained
from the slope of the red giant branch. However, we confirm previous
determinations for Hodge 11 and NGC 1898 to within 0.2 dex. The LMC cluster
[Mg/Fe] and [Si/Fe] ratios are comparable to the values observed in old
Galactic globular cluster stars, as are the abundances [Y/Fe], [Ba/Fe], and
[Eu/Fe]. The LMC clusters do not share the low-Y behavior observed in some
dwarf spheroidal galaxies. [Ca/Fe], [Ti/Fe], and [V/Fe] in the LMC, however,
are significantly lower than what is seen in the Galactic globular cluster
system. Neither does the behavior of [Cu/Fe] as a function of [Fe/H] in our LMC
clusters match the trend seen in the Galaxy, staying instead at a constant
value of ~0.8. Because not all [alpha/Fe] ratios are suppressed, these
abundance ratios cannot be attributed solely to the injection of Type Ia SNe
material, and instead reflect the differences in star formation history of the
LMC vs. the Milky Way. We conclude that many of the abundances in the LMC
globular clusters we observed are distinct from those observed in the Milky
Way, and these differences are intrinsic to the stars in those systems.Comment: To be published in ApJ, 21 pages, 12 figures. Tables 2 (equivalent
widths) and 3 (hyperfine splitting information) included separatel
Health system responsiveness to the mental health needs of Syrian refugees: mixed-methods rapid appraisals in eight host countries in Europe and the Middle East
Background: Syrian refugees have a high burden of mental health symptoms and face challenges in accessing mental health and psychosocial support (MHPSS). This study assesses health system responsiveness (HSR) to the MHPSS needs of Syrian refugees, comparing countries in Europe and the Middle East to inform recommendations for strengthening MHPSS systems. Methods: A mixed-methods rapid appraisal methodology guided by an adapted WHO Health System Framework was used to assess HSR in eight countries (Egypt, Germany, Jordan, Lebanon, Netherlands, Sweden, Switzerland, and Türkiye). Quantitative and qualitative analysis of primary and secondary data was used. Data collection and analysis were performed iteratively by multiple researchers. Country reports were used for comparative analysis and synthesis. Results: We found numerous constraints in HSR: i) Too few appropriate mental health providers and services; ii) Travel-related barriers impeding access to services, widening rural-urban inequalities in the distribution of mental health workers; iii) Cultural, language, and knowledge-related barriers to timely care likely caused by insufficient numbers of culturally sensitive providers, costs of professional interpreters, somatic presentations of distress by Syrian refugees, limited mental health awareness, and stigma associated to mental illness; iv) High out-of-pocket costs for psychological treatment and transportation to services reducing affordability, particularly in middle-income countries; v) Long waiting times for specialist mental health services; vi) Information gaps on the mental health needs of refugees and responsiveness of MHPSS systems in all countries. Six recommendations are provided. Conclusions: All eight host countries struggle to provide responsive MHPSS to Syrian refugees. Strengthening the mental health workforce (in terms of quantity, quality, diversity, and distribution) is urgently needed to enable Syrian refugees to receive culturally appropriate and timely care and improve mental health outcomes. Increased financial investment in mental health and improved health information systems are crucial
Abundances of 30 elements in 23 metal-poor stars
We report the abundances of 30 elements in 23 metal-poor ([Fe/H] <-1.7)
giants. These are based on 7774 equivalent widths and spectral synthesis of 229
additional lines. Hyperfine splitting is taken into account when appropriate.
Our choice of model atmospheres has the most influence on the accuracy of our
abundances. We consider the effect of different model atmospheres on our
results. In addition to the random errors in Teff, log g, and microturbulent
velocity, there are several sources of systematic error. These include using
Teff determined from FeI lines rather than colors, ignoring NLTE effects on the
FeI/FeII ionization balance, using models with solar [alpha/Fe] ratios and
using Kurucz models with overshooting. Of these, only the use of models with
solar [alpha/Fe] ratios had a negligible effect. However, while the absolute
abundances can change by > 0.10 dex, the relative abundances, especially
between closely allied atoms such as the rare earth group, often show only
small (<0.03 dex) changes. We found that some strong lines of FeI, MnI and CrI
consistently gave lower abundances by ~0.2 dex, a number larger than the quoted
errors in the gf values. After considering a model with depth-dependent
microturbulent velocity and a model with hotter temperatures in the upper
layers, we conclude that the latter did a better job of resolving the problem
and agreeing with observational evidence for the structure of stars. The error
analysis includes the effects of correlation of Teff, log g, and microturbulent
velocity errors, which is crucial for certain element ratios, such as [Mg/Fe].
The abundances presented here are being analyzed and discussed in a separate
series of papers.Comment: 27 pages, 9 figures, Table 2 included separately, to published in
ApJ
Trace elements in glucometabolic disorders: an update
Many trace elements, among which metals, are indispensable for proper functioning of a myriad of biochemical reactions, more particularly as enzyme cofactors. This is particularly true for the vast set of processes involved in regulation of glucose homeostasis, being it in glucose metabolism itself or in hormonal control, especially insulin. The role and importance of trace elements such as chromium, zinc, selenium, lithium and vanadium are much less evident and subjected to chronic debate. This review updates our actual knowledge concerning these five trace elements. A careful survey of the literature shows that while theoretical postulates from some key roles of these elements had led to real hopes for therapy of insulin resistance and diabetes, the limited experience based on available data indicates that beneficial effects and use of most of them are subjected to caution, given the narrow window between safe and unsafe doses. Clear therapeutic benefit in these pathologies is presently doubtful but some data indicate that these metals may have a clinical interest in patients presenting deficiencies in individual metal levels. The same holds true for an association of some trace elements such as chromium or zinc with oral antidiabetics. However, this area is essentially unexplored in adequate clinical trials, which are worth being performed
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